The present invention relates to a process for preparing a molding element for motorcar bodies.
In particular, the molding element in reference is intended for being applied as finish and/or protection to motorcar bodies and more specifically to parts thereof such as doors, bumpers, edge areas at the lower perimeter of the car body, and so on.
It is known that molding elements for uses as briefly described above are traditionally comprised of a strip, typically of plastic material, which is provided with appropriate attachment means for association with the intended body portion.
In particular, presently there are different typologies of molding elements depending on the different attachment systems used for anchoring to the car body.
In a first known typology of molding elements, the strip of plastic material is anchored by use of adhesives and more specifically double-sided adhesive tapes interposed between the car body and one side of the molding element.
Drawbacks of this type of anchoring are well apparent: precariousness in connection, unreliability in time, great responsiveness to weathering and dynamic stresses.
In a second type of known typology, the attachment means consists of nails or studs fastened, by welding for example, to the car body and suitably covered with plastic material so that they can be fitted, by snap or interference fit, into corresponding housings formed in a coupling face of the molding element.
Surely, this second type of known typology is more reliable than the previously described one. However, it is to note that, due to the fact that a plurality of nails or studs are to be made and connected to the car body, a great complication in terms of construction is involved and necessarily lack of precision may occur in working which, in conclusion, will bring about high production costs and often poor quality of the product. More precisely, possible lack of precision in the size and/or placement of the attachment nails or studs gives rise to an inappropriate fastening of the strip or molding element and consequent deformation of same, which will give rise to an irreparable lack of levelness and reduced respect of geometric tolerances, in particular with reference to the outer surface of the molding element. These consequences are clearly unacceptable from an aesthetic point of view.
In an attempt to solve the mentioned drawbacks, a third typology of molding elements has been recently widespread, in which the molding element has a longitudinal housing intended for receiving, by snap-fitting, a plurality of coupling elements which are positioned in the longitudinal housing at locations spaced apart the same distance from each other.
More specifically, the molding element comprises an elongated main body, to be obtained by extrusion or molding, in which the longitudinal housing is defined. Said housing, on the molding element side to be turned to the car body, has an opening or slit from which the coupling element can partly emerge. In more detail, at the opening or slit, millings or cuttings are formed at regular intervals so as to enable insertion of each of the coupling elements while at the same time defining axial locating surfaces into which the coupling elements are snap-locked.
The different coupling elements, once they have been suitably linked to each other, will each have at least one projection emerging in a direction substantially perpendicular to the longitudinal housing in order to engage corresponding slots formed in the car body.
Although the last mentioned construction of known type is surely valid as regards anchoring and operating reliability, it has shown important drawbacks too.
In particular, since millings are to be executed at the longitudinal housing for access of the coupling elements, an additional working step is clearly involved which will bring about additional production costs. Furthermore, since the main body in which milling is carried out is typically made of a material having good mechanical features, and sometimes is even made of two materials, milling operations are not easy.
It is also to note that milling or cutting operations give rise to an important weakening in the structure forming the molding element, thereby inevitably involving deformations and in particular surely unaesthetical undulations that reduce levelness and observance of the geometrical tolerances in the outer surface of the molding element. Furthermore, due to the great rigidity of the section member and the presence in many cases of metal cores, problems may arise in carrying out maintenance of the abrasive elements for executing the milling operations, which will result in high working costs and product waste.
In addition, the residual presence of possible burrs can cause abrasions and scratches on the painted portions of the car body.